Interface force feedback in a laser eye surgery system

ABSTRACT

The patient interface may comprise an axis for alignment with an axis of the eye such as an optical axis of the eye. The interface may comprise a guide to allow the interface to move along the axis with the eye, which can inhibit increases in intraocular pressure when the patient is aligned with the laser. The interface may comprise a lock to hold the patient interface at a location along the axis, which can maintain alignment of the patient with the laser eye surgery system. The interface may comprise a plurality of transducers to measure forces to the eye during surgery. The laser eye surgery system can be configured in one or more of many ways to respond to the measured forces. For example, the system may offset the position of laser beam pulses to increase the accuracy of the placement of the beam pulses on the eye.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No.: 61/721,709, filed Nov. 2, 2012.

BACKGROUND

The present disclosure relates generally to laser eye surgery. Althoughspecific reference is made to cataract surgery, the methods andapparatus described herein can be used with many surgical procedures ofthe eye and other tissues.

Many surgical procedures can be performed on patients, includingophthalmic surgery. Opthalmic surgery can include surgery on one or moreof the cornea, the lens or the retina, for example.

Cataract extraction is a commonly performed surgical procedure. Acataract is formed by opacification of the crystalline lens or itsenvelope—the lens capsule—of the eye. The cataract obstructs passage oflight through the lens. A cataract can vary in degree from slight tocomplete opacity. Early in the development of an age-related cataractthe power of the lens may be increased, causing near-sightedness(myopia). Gradual yellowing and opacification of the lens may reduce theperception of blue colors as those wavelengths are absorbed andscattered within the crystalline lens. Cataract formation typicallyprogresses slowly resulting in progressive vision loss. Cataracts arepotentially blinding if untreated.

A common cataract treatment involves replacing the opaque crystallinelens with an artificial intraocular lens (IOL). An estimated 15 millioncataract surgeries per year are performed worldwide. The cataracttreatment market is composed of various segments including intraocularlenses for implantation, viscoelastic polymers to facilitate surgicalprocedures, and disposable instrumentation including ultrasonicphacoemulsification tips, tubing, various knives, and forceps.

Cataract surgery is typically performed using a technique termedphacoemulsification in which an ultrasonic tip with associatedirrigation and aspiration ports is used to sculpt the relatively hardnucleus of the lens to facilitate removal through an opening made in theanterior lens capsule. The nucleus of the lens is contained within anouter membrane of the lens that is referred to as the lens capsule.Access to the lens nucleus can be provided by performing an anteriorcapsulotomy in which a small (often round) hole is formed in theanterior side of the lens capsule. Access to the lens nucleus can alsobe provided by performing a manual continuous curvilinear capsulorhexis(CCC) procedure. After removal of the lens nucleus, a synthetic foldableintraocular lens (IOL) can be inserted into the remaining lens capsuleof the eye. Typically, the IOL is held in place by the edges of theanterior capsule and the capsular bag. The IOL may also be held by theposterior capsule, either alone or in unison with the anterior capsule.This latter configuration is known in the field as a “Bag-in-Lens”implant.

One of the most technically challenging and critical steps in thecataract extraction procedure is providing access to the lens nucleus.The manual continuous curvilinear capsulorhexis (CCC) procedure evolvedfrom an earlier technique termed can-opener capsulotomy in which a sharpneedle was used to perforate the anterior lens capsule in a circularfashion followed by the removal of a circular fragment of lens capsuletypically in the range of 5-8 mm in diameter. The smaller thecapsulotomy, the more difficult it is to produce manually. Thecapsulotomy provides access for the next step of nuclear sculpting byphacoemulsification. Due to a variety of complications associated withthe initial can-opener technique, attempts were made by leading expertsin the field to develop a better technique for removal of the circularfragment of the anterior lens capsule prior to the emulsification step.

The desired outcome of the manual continuous curvilinear capsulorhexisis to provide a smooth continuous circular opening through which notonly the phacoemulsification of the nucleus can be performed safely andeasily, but also to provide for easy insertion of the intraocular lens.The resulting opening in the anterior lens capsule provides access fortool insertion during removal of the nucleus and for IOL insertion, apermanent aperture for transmission of the image to the retina of thepatient, and also support of the IOL inside the remaining lens capsulethat limits the potential for dislocation. The resulting reliance on theshape, symmetry, uniformity, and strength of the remaining lens capsuleto contain, constrain, position, and maintain the IOL in the patient'seye limits the placement accuracy of the IOL, both initially and overtime. Subsequently, a patient's refractive outcome and resultant visualacuity are less deterministic and intrinsically sub-optimal due to theIOL placement uncertainty. This is especially true for astigmatismcorrecting (“toric”) and accommodating (“presbyopic”) IOLs.

Problems may also develop related to inability of the surgeon toadequately visualize the lens capsule due to lack of red reflex, tograsp the lens capsule with sufficient security, and to tear a smoothcircular opening in the lens capsule of the appropriate size and in thecorrect location without creating radial rips and extensions. Alsopresent are technical difficulties related to maintenance of the depthof the anterior chamber depth after opening the lens capsule, smallpupils, or the absence of a red reflex due to the lens opacity. Some ofthe problems with visualization can be minimized through the use of dyessuch as methylene blue or indocyanine green. Additional complicationsmay also arise in patients with weak zonules (typically older patients)and very young children that have very soft and elastic lens capsules,which are very difficult to controllably and reliably rupture and tear.

The implantation of a “Bag-in-Lens” IOL typically uses anterior andposterior openings in the lens capsule of the same size. Manuallycreating matching anterior and posterior capsulotomies for the“Bag-in-Lens” configuration, however, is particularly difficult.

Many patients have astigmatic visual errors. Astigmatism can occur whenthe corneal curvature is unequal in two or more directions. InAstigmatic Keratotomy, Corneal Relaxing Incision (CRI), and LimbalRelaxing Incision (LRI), corneal incisions are made in a well-definedmanner and depth to allow the cornea to change shape to become morespherical. These corneal incisions can accomplished manually but oftenwith limited precision.

Although pulsed lasers have been proposed to treat eyes having cataractsand/or refractive errors, coupling of the prior patient interfaces canlead to less than ideal results in at least some instances. A patientinterface can be provided to couple the laser beam to the eye toposition the depth of the treatment within the eye at an intendedlocation. However, the prior patient interfaces may provide less thanideal coupling of the eye to the laser. For example, prior patientinterfaces can provide less than ideal increases in intra ocularpressure (hereinafter “IOP”). Also, the prior patient interfaces can besomewhat cumbersome for users of the system and the patients in at leastsome instances. Also, the prior patient interfaces can be somewhat rigidand intolerant of patient movement which may lead to decoupling of theinterface and a partially completed treatment such that the priorpatient interfaces may provide a less than ideal surgical experience inat least some instances.

Thus, improved methods and systems for treating are needed.

SUMMARY

Improved patient interface methods and apparatus are provided, which canfacilitate alignment of the patient to the laser system and inhibitincreases in intra-ocular pressure of the eye. The surgical laser systemas described herein may comprise a patient interface assembly configuredto inhibit increases of intraocular pressure during surgery, facilitatealignment during surgery, and can provide improved alignment of thepatient. The patient interface may comprise an axis for alignment withan axis of the eye such as an optical axis of the eye. The patientinterface may comprise a guide to allow the patient interface to movealong the axis with the eye, which can inhibit increases in intraocularpressure when the patient is aligned with the laser. The patientinterface may comprise a lock to hold the patient interface at alocation along the axis, which can maintain alignment of the patientwith the laser eye surgery system. The patient interface may comprise aplurality of transducers to measure forces to the eye during surgery,and the laser eye surgery system can be configured in one or more ofmany ways to respond to the measured forces. The laser eye surgerysystem may offset the position of the laser beam pulses in response tothe measured forces to increase the accuracy of the placement of thelaser beam pulses on the eye. The laser surgery system may limitmovement of the patient in response to the forces to the eye, and mayprovide the measured forces to the user. In many embodiments, thepatient interface may comprise a compliance that allows the eye to movewhen coupled to the interface so as to decrease pressure to the eye, andthe laser eye surgery system can offset the laser beam pulses in one ormore of three dimensions in response to the measured forces and thecompliance so as to increase accuracy of the focused laser beam on theeye.

In a first aspect, a laser eye surgery comprising a patient support, apatient interface, and a controller is provided. The patient interfacecouples to the eye of a patient and comprises an axis alignable with theeye of the patient. The patient interface further comprises a pluralityof force transducers to monitor forces between the eye of the patientand the patient interface. The controller is coupled to the support tomove the at least one of the patient support or the patient interface inresponse to the monitored forces. The patient support or the patientinterface can be moved along the axis and transverse to the axis. Inmany embodiments, the patient support is moved while the patientinterface remains stationary or vice versa. Typically, the patientsupport will be moved while the patient interface remains stationary.

The patient support will typically comprise a base and a linkage to movethe patient support along the axis and transverse to the axis inresponse to the controller. For instance, the patient support maycomprise a moveable patient chair having a patient seating area moveablerelative to the base.

There will typically be at least three force transducers coupled to thecontroller. Each force transducer monitors a force between the eye ofthe patient and the patient interface. Typically, the controller isconfigured to receive the force from each of the force transducers anddetermine (1) a force along the axis of the patient interface, (2) afirst force in a first direction transverse to the axis, and (3) asecond force in a second direction transverse to the axis, i.e., forcesalong the X, Y, and Z axes. The laser eye surgery system may furthercomprise a display for displaying the calculated forces along the axis,the first direction, and the second direction as a three dimensionalvector. The controller may embody instructions of a program to move thepatient support along X, Y, and Z axes in response to the calculatedforces so as to maintain the forces between the eye of the patient andthe patient interface within a desired range. The controller may alsoembody instructions of a program to offset pulses of the laser beam inresponse to forces of the plurality of transducers or to allow movementof the patient support along the X and Y directions transverse to the Zaxis to decrease force to the eye.

The laser eye surgery system may further comprise a counter-weightcoupled to the patient interface. The counter-weight facilitatesvertical movement of the patient interface.

In many embodiments, the axis of the patient interface extends in avertical direction and the patient interface is adapted to move upwardby upward movement of the patient support when the patient is placed onthe patient support and the eye of the patient is coupled to the patientinterface.

The laser eye surgery system may comprise a locking mechanism adapted tolock the vertical position of the patient interface when the patientinterface has reached a desired vertical position. The locking mechanismmay comprise one or more of a detent, a lock and key mechanism, anopening to receive a linear protrusion, a rotating cam, or a flatsurface to receive a friction brake.

In another aspect, a method of coupling an eye of a patient relative toa patient interface is provided. The patient is placed on a moveablepatient support; the eye of the patient is coupled to the patientinterface to align an axis of the patient interface with the eye; andthe patient support is moved along the axis with the eye to position thepatient interface for surgery. Often, a vertical position of the patientinterface is tracked and the upward movement of the moveable patientsupport is limited based on the tracked vertical position of the patientinterface.

The eye may be coupled to the patient interface by coupling a suctionring to the eye and coupling the suction ring to a disposable lens conecoupled to the patient interface.

The patient interface will typically be locked in place once the patientsupport has reached the desired vertical position. When the patientinterface has been locked in place, upward movement of the moveablepatient support will typically be limited by preventing any furtherupward movement of the moveable patient support. The lateral movement ofthe moveable patient support will typically be unrestricted while theupward movement of the moveable patient support is limited. In someembodiments, however, the lateral position of the patient interface istracked and lateral movement of the patient support is limited based onthis tracked lateral position.

In another aspect, a method of stabilizing an eye of a patient relativeto a patient interface of a laser eye surgery system is provided. Apatient is placed on a top side of a moveable patient support of thelaser eye surgery system; the eye is coupled to the patient interfacepositioned above the eye; vertical forces are monitored between thepatient interface and the eye; and the patient interface is moved withthe eye to position the interface and the eye for surgery. The eye willtypically be coupled to the patient interface by coupling a suction ringto the eye and coupling the suction ring to a disposable lens conecoupled to the patient interface. The monitored vertical forces willoften be displayed on a display coupled to the laser eye surgery system.

Generally, the patient interface moves vertically while maintaining asubstantially constant vertical force between the patient interface andthe eye. Vertically moving the patient support may comprise operating auser controlled control element of the laser eye surgery system tovertically move the patient interface based on the displayed verticalforces. The user controlled control element may be, for example, a joystick or a touch screen control panel. In many embodiments, the patientsupport is instead automatically moved based on the monitored verticalforces to maintain constant vertical force between the patient interfaceand the eye.

The provided method may further comprise a step of calculating lateralforces between the patient interface and the eye based on the monitoredvertical forces. The patient support may be moved laterally to maintainthe lateral forces within a desired range. The calculated lateral forceswill often be displayed on a display coupled to the laser eye surgerysystem. To keep the lateral forces within a desired range, an operatorof the laser eye surgery system may operate a user controlled controlelement of the laser eye surgery system to laterally move the patientinterface based on the displayed lateral forces. The user controlledcontrol element may comprise, for example, a joystick or a touch screencontrol panel. In many embodiments, the patient support is insteadautomatically moved based on the calculated lateral forces to keep thelateral forces within a desired range.

In another aspect, a method of treating an eye of a patient is provided.The patient is placed on a moveable patient support; the eye is coupledto a patient interface of a laser eye surgery system; forces aremeasured between the patient interface and the eye; determining movementof the eye location is determined based on the measured forces andstiffness of the patient interface; and laser target locations areadjusted based on the determined movement. Movement of the eye may bedetermined by determining movement of a targeted location of the eye andcalculating relative movement of the targeted location of the eye basedon the eye's stiffness characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present disclosure are set forth with particularityin the appended claims. A better understanding of the features andadvantages of the present disclosure will be obtained by reference tothe following detailed description that sets forth illustrativeembodiments, in which the principles of the disclosure are utilized, andthe accompanying drawings of which:

FIG. 1 is a perspective view showing a laser eye surgery system, inaccordance with many embodiments.

FIG. 2 is a simplified block diagram showing a top level view of theconfiguration of a laser eye surgery system, in accordance with manyembodiments.

FIG. 3 is a simplified block diagram illustrating the configuration ofan optical assembly of a laser eye surgery system, in accordance withmany embodiments.

FIG. 4 is a flow chart illustrating a procedure to secure the positionof the patient's eye relative to the patient interface, in accordancewith many embodiments.

FIGS. 5A-5E show the securing of the position of the patient's eyerelative to the patient interface, in accordance with many embodiments.

FIG. 6 shows a cross-section of the patient interface, in accordancewith many embodiments.

FIG. 7 is a simplified block diagram of a subsystem to monitor andcontrol the position of the patient's eye relative to the patientinterface, in accordance with many embodiments.

FIG. 8 is a flow chart illustrating a procedure to adjust the laser eyesurgery system, in accordance with many embodiments.

FIG. 9 is a flow chart illustrating a procedure to secure the positionof the patient's eye relative to the patient interface, in accordancewith many embodiments.

DETAILED DESCRIPTION

Methods and systems related to laser eye surgery are disclosed. A laseris used to form precise incisions in the cornea, in the lens capsule,and/or in the crystalline lens nucleus, for example. The embodiments ofthe present disclosure as described herein are particularly well suitedfor beneficial combination with one or more surgical procedures such ascataract surgery, refractive surgery, retinal surgery, intraocularlenses, intracorneal lenses, corneal sculpting, Laser-Assisted in SituKeratomileusis (hereafter “LASIK”), or laser-assisted subepithelialkeratomileusis (hereinafter “LASEK), and combinations thereof, forexample. The surgical laser system as described herein may comprise apatient interface assembly configured to inhibit increases ofintraocular pressure during surgery, can facilitate alignment duringsurgery, and can provide improved alignment of the patient. The patientinterface may comprise an axis for alignment with an axis of the eyesuch as an optical axis of the eye. The patient interface may comprise aguide to allow the patient interface to move along the axis with theeye. The patient interface may comprise a lock to hold the patientinterface at a location along the axis. The patient interface maycomprise a plurality of transducers to measure forces to the eye duringsurgery, and the laser surgery system can limit movement of the patientin response to the forces to the eye, and may offset the position of thelaser beam pulses in response to the measured forces.

System Configuration

FIG. 1 shows a laser eye surgery system 2, in accordance with manyembodiments, operable to form precise incisions in the cornea, in thelens capsule, and/or in the crystalline lens nucleus. The system 2includes a main unit 4, a patient chair 6, a dual function footswitch 8,and a laser footswitch 10.

The main unit 4 includes many primary subsystems of the system 2. Forexample, externally visible subsystems include a touch-screen controlpanel 12, a patient interface assembly 14, patient interface vacuumconnections 16, a docking control keypad 18, a patient interface radiofrequency identification (RFID) reader 20, external connections 22(e.g., network, video output, footswitch, USB port, door interlock, andAC power), laser emission indicator 24, emergency laser stop button 26,key switch 28, and USB data ports 30.

The patient chair 6 includes a base 32, a patient support bed 34, aheadrest 36, a positioning mechanism, and a patient chair joystickcontrol 38 disposed on the headrest 36. The positioning controlmechanism is coupled between the base 32 and the patient support bed 34and headrest 36. The patient chair 6 is configured to be adjusted andoriented in three axes (x, y, and z) using the patient chair joystickcontrol 38. The headrest 36 and a restrain system (not shown, e.g., arestraint strap engaging the patient's forehead) stabilize the patient'shead during the procedure. The headrest 36 includes an adjustable necksupport to provide patient comfort and to reduce patient head movement.The headrest 36 is configured to be vertically adjustable to enableadjustment of the patient head position to provide patient comfort andto accommodate variation in patient head size.

The patient chair 6 allows for tilt articulation of the patient's legs,torso, and head using manual adjustments. The patient chair 6accommodates a patient load position, a suction ring capture position,and a patient treat position. In the patient load position, the chair 6is rotated out from under the main unit 4 with the patient chair back inan upright position and patient footrest in a lowered position. In thesuction ring capture position, the chair is rotated out from under themain unit 4 with the patient chair back in reclined position and patientfootrest in raised position. In the patient treat position, the chair isrotated under the main unit 4 with the patient chair back in reclinedposition and patient footrest in raised position.

The patient chair 6 is equipped with a “chair enable” feature to protectagainst unintended chair motion. The patient chair joystick 38 can beenabled in either of two ways. First, the patient chair joystick 38incorporates a “chair enable” button located on the top of the joystick.Control of the position of the patient chair 6 via the joystick 38 canbe enabled by continuously pressing the “chair enable” button.Alternately, the left foot switch 40 of the dual function footswitch 8can be continuously depressed to enable positional control of thepatient chair 6 via the joystick 38. To further protect againstunintended chair motion, power supplied to the patient chair 6 mayautomatically be cut off using a switch.

In many embodiments, the patient control joystick 38 is a proportionalcontroller. For example, moving the joystick a small amount can be usedto cause the chair to move slowly. Moving the joystick a large amountcan be used to cause the chair to move faster. Holding the joystick atits maximum travel limit can be used to cause the chair to move at themaximum chair speed. The available chair speed can be reduced as thepatient approaches the patient interface assembly 14.

The emergency stop button 26 can be pushed to stop emission of all laseroutput, release vacuum that couples the patient to the system 2, anddisable the patient chair 6. The stop button 26 is located on the systemfront panel, next to the key switch 28.

The key switch 28 can be used to enable the system 2. When in a standbyposition, the key can be removed and the system is disabled. When in aready position, the key enables power to the system 2.

The dual function footswitch 8 is a dual footswitch assembly thatincludes the left foot switch 40 and a right foot switch 42. The leftfoot switch 40 is the “chair enable” footswitch. The right footswitch 42is a “vacuum ON” footswitch that enables vacuum to secure a liquidoptics interface suction ring to the patient's eye. The laser footswitch10 is a shrouded footswitch that activates the treatment laser whendepressed while the system is enabled.

In many embodiments, the system 2 includes external communicationconnections. For example, the system 2 can include a network connection(e.g., an RJ45 network connection) for connecting the system 2 to anetwork. The network connection can be used to enable network printingof treatment reports, remote access to view system performance logs, andremote access to perform system diagnostics. The system 2 can include avideo output port (e.g., HDMI) that can be used to output video oftreatments performed by the system 2. The output video can be displayedon an external monitor for, for example, viewing by family membersand/or training. The output video can also be recorded for, for example,archival purposes. The system 2 can include one or more data outputports (e.g., USB) to, for example, enable export of treatment reports toa data storage device. The treatments reports stored on the data storagedevice can then be accessed at a later time for any suitable purposesuch as, for example, printing from an external computer in the casewhere the user is without access to network based printing.

FIG. 2 shows a simplified block diagram of the system 2 coupled with apatient eye 43. The patient eye 43 comprises a cornea, a lens, and aniris. The iris defines a pupil of the eye 43 that may be used foralignment of eye 43 with system 2. The system 2 includes a cutting lasersubsystem 44, a ranging subsystem 46, an alignment guidance system 48,shared optics 50, a patient interface 52, control electronics 54, acontrol panel/GUI 56, user interface devices 58, and communication paths60. The control electronics 54 is operatively coupled via thecommunication paths 60 with the cutting laser subsystem 44, the rangingsubsystem 46, the alignment guidance subsystem 48, the shared optics 50,the patient interface 52, the control panel/GUI 56, and the userinterface devices 58.

In many embodiments, the cutting laser subsystem 44 incorporatesfemtosecond (FS) laser technology. By using femtosecond lasertechnology, a short duration (e.g., approximately 10⁻¹³ seconds induration) laser pulse (with energy level in the micro joule range) canbe delivered to a tightly focused point to disrupt tissue, therebysubstantially lowering the energy level required as compared to thelevel required for ultrasound fragmentation of the lens nucleus and ascompared to laser pulses having longer durations.

The cutting laser subsystem 44 can produce laser pulses having awavelength suitable to the configuration of the system 2. As anon-limiting example, the system 2 can be configured to use a cuttinglaser subsystem 44 that produces laser pulses having a wavelength from1020 nm to 1050 nm. For example, the cutting laser subsystem 44 can havea diode-pumped solid-state configuration with a 1030 (+/−5) nm centerwavelength.

The cutting laser subsystem 44 can include control and conditioningcomponents. For example, such control components can include componentssuch as a beam attenuator to control the energy of the laser pulse andthe average power of the pulse train, a fixed aperture to control thecross-sectional spatial extent of the beam containing the laser pulses,one or more power monitors to monitor the flux and repetition rate ofthe beam train and therefore the energy of the laser pulses, and ashutter to allow/block transmission of the laser pulses. Suchconditioning components can include an adjustable zoom assembly to adaptthe beam containing the laser pulses to the characteristics of thesystem 2 and a fixed optical relay to transfer the laser pulses over adistance while accommodating laser pulse beam positional and/ordirectional variability, thereby providing increased tolerance forcomponent variation.

The ranging subsystem 46 is configured to measure the spatialdisposition of eye structures in three dimensions. The measured eyestructures can include the anterior and posterior surfaces of thecornea, the anterior and posterior portions of the lens capsule, theiris, and the limbus. In many embodiments, the ranging subsystem 46utilizes optical coherence tomography (OCT) imaging. As a non-limitingexample, the system 2 can be configured to use an OCT imaging systememploying wavelengths from 780 nm to 970 nm. For example, the rangingsubsystem 46 can include an OCT imaging system that employs a broadspectrum of wavelengths from 810 nm to 850 nm. Such an OCT imagingsystem can employ a reference path length that is adjustable to adjustthe effective depth in the eye of the OCT measurement, thereby allowingthe measurement of system components including features of the patientinterface that lie anterior to the cornea of the eye and structures ofthe eye that range in depth from the anterior surface of the cornea tothe posterior portion of the lens capsule and beyond.

The alignment guidance subsystem 48 can include a laser diode or gaslaser that produces a laser beam used to align optical components of thesystem 2. The alignment guidance subsystem 48 can include LEDs or lasersthat produce a fixation light to assist in aligning and stabilizing thepatient's eye during docking and treatment. The alignment guidancesubsystem 48 can include a laser or LED light source and a detector tomonitor the alignment and stability of the actuators used to positionthe beam in X, Y, and Z. The alignment guidance subsystem 48 can includea video system that can be used to provide imaging of the patient's eyeto facilitate docking of the patient's eye 43 to the patient interface52. The imaging system provided by the video system can also be used todirect via the GUI the location of cuts. The imaging provided by thevideo system can additionally be used during the laser eye surgeryprocedure to monitor the progress of the procedure, to track movementsof the patient's eye 43 during the procedure, and to measure thelocation and size of structures of the eye such as the pupil and/orlimbus.

The shared optics 50 provides a common propagation path that is disposedbetween the patient interface 52 and each of the cutting laser subsystem44, the ranging subsystem 46, and the alignment guidance subsystem 48.In many embodiments, the shared optics 50 includes beam combiners toreceive the emission from the respective subsystem (e.g., the cuttinglaser subsystem 44, the ranging subsystem 46, and the alignment guidancesubsystem 48) and redirect the emission along the common propagationpath to the patient interface. In many embodiments, the shared optics 50includes an objective lens assembly that focuses each laser pulse into afocal point. In many embodiments, the shared optics 50 includes scanningmechanisms operable to scan the respective emission in three dimensions.For example, the shared optics can include an XY-scan mechanism(s) and aZ-scan mechanism. The XY-scan mechanism(s) can be used to scan therespective emission in two dimensions transverse to the propagationdirection of the respective emission. The Z-scan mechanism can be usedto vary the depth of the focal point within the eye 43. In manyembodiments, the scanning mechanisms are disposed between the laserdiode and the objective lens such that the scanning mechanisms are usedto scan the alignment laser beam produced by the laser diode. Incontrast, in many embodiments, the video system is disposed between thescanning mechanisms and the objective lens such that the scanningmechanisms do not affect the image obtained by the video system.

The patient interface 52 is used to restrain the position of thepatient's eye 43 relative to the system 2. In many embodiments, thepatient interface 52 employs a suction ring that is vacuum attached tothe patient's eye 43. The suction ring is then coupled with the patientinterface 52, for example, using vacuum to secure the suction ring tothe patient interface 52. In many embodiments, the patient interface 52includes an optically transmissive structure having a posterior surfacethat is displaced vertically from the anterior surface of the patient'scornea and a region of a suitable liquid (e.g., a sterile bufferedsaline solution (BSS) such as Alcon BSS (Alcon Part Number 351-55005-1)or equivalent) is disposed between and in contact with the posteriorsurface and the patient's cornea and forms part of a transmission pathbetween the shared optics 50 and the patient's eye 43. The opticallytransmissive structure may comprise a lens 96 having one or more curvedsurfaces. Alternatively, the patient interface 22 may comprise anoptically transmissive structure having one or more substantially flatsurfaces such as a parallel plate or wedge. In many embodiments, thepatient interface lens is disposable and can be replaced at any suitableinterval, such as before each eye treatment.

The control electronics 54 controls the operation of and can receiveinput from the cutting laser subsystem 44, the ranging subsystem 46, thealignment guidance subsystem 48, the patient interface 52, the controlpanel/GUI 56, and the user interface devices 58 via the communicationpaths 60. The communication paths 60 can be implemented in any suitableconfiguration, including any suitable shared or dedicated communicationpaths between the control electronics 54 and the respective systemcomponents.

The control electronics 54 can include any suitable components, such asone or more processor, one or more field-programmable gate array (FPGA),and one or more memory storage devices. In many embodiments, the controlelectronics 54 controls the control panel/GUI 56 to provide forpre-procedure planning according to user specified treatment parametersas well as to provide user control over the laser eye surgery procedure.

The control electronics 54 may comprise a processor/controller 55(referred to herein as a processor) that is used to perform calculationsrelated to system operation and provide control signals to the varioussystem elements. A computer readable medium 57 (also referred to as adatabase or a memory) is coupled to the processor 55 in order to storedata used by the processor and other system elements. The processor 55interacts with the other components of the system as described morefully throughout the present specification. In an embodiment, the memory57 can include a look up table that can be utilized to control one ormore components of the laser system as described herein.

The processor 55 can be a general purpose microprocessor configured toexecute instructions and data, such as a Pentium processor manufacturedby the Intel Corporation of Santa Clara, Calif. It can also be anApplication Specific Integrated Circuit (ASIC) that embodies at leastpart of the instructions for performing the method in accordance withthe embodiments of the present disclosure in software, firmware and/orhardware. As an example, such processors include dedicated circuitry,ASICs, combinatorial logic, other programmable processors, combinationsthereof, and the like.

The memory 57 can be local or distributed as appropriate to theparticular application. Memory 57 may include a number of memoriesincluding a main random access memory (RAM) for storage of instructionsand data during program execution and a read only memory (ROM) in whichfixed instructions are stored. Thus, memory 57 provides persistent(non-volatile) storage for program and data files, and may include ahard disk drive, flash memory, a floppy disk drive along with associatedremovable media, a Compact Disk Read Only Memory (CD-ROM) drive, anoptical drive, removable media cartridges, and other like storage media.

The user interface devices 58 can include any suitable user input devicesuitable to provide user input to the control electronics 54. Forexample, the user interface devices 58 can include devices such as, forexample, the dual function footswitch 8, the laser footswitch 10, thedocking control keypad 18, the patient interface radio frequencyidentification (RFID) reader 20, the emergency laser stop button 26, thekey switch 28, and the patient chair joystick control 38.

FIG. 3 is a simplified block diagram illustrating an assembly 62, inaccordance with many embodiments, that can be included in the system 2.The assembly 62 is a non-limiting example of suitable configurations andintegration of the cutting laser subsystem 44, the ranging subsystem 46,the alignment guidance subsystem 48, the shared optics 50, and thepatient interface 52. Other configurations and integration of thecutting laser subsystem 44, the ranging subsystem 46, the alignmentguidance subsystem 48, the shared optics 50, and the patient interface52 may be possible and may be apparent to a person of skill in the art.

The assembly 62 is operable to project and scan optical beams into thepatient's eye 43. The cutting laser subsystem 44 includes an ultrafast(UF) laser 64 (e.g., a femtosecond laser). Using the assembly 62,optical beams can be scanned in the patient's eye 43 in threedimensions: X, Y, Z. For example, short-pulsed laser light generated bythe UF laser 64 can be focused into eye tissue to produce dielectricbreakdown to cause photodisruption around the focal point (the focalzone), thereby rupturing the tissue in the vicinity of the photo-inducedplasma. In the assembly 62, the wavelength of the laser light can varybetween 800 nm to 1200 nm and the pulse width of the laser light canvary from 10 fs to 10000 fs. The pulse repetition frequency can alsovary from 10 kHz to 500 kHz. Safety limits with regard to unintendeddamage to non-targeted tissue bound the upper limit with regard torepetition rate and pulse energy. Threshold energy, time to complete theprocedure, and stability can bound the lower limit for pulse energy andrepetition rate. The peak power of the focused spot in the eye 43 andspecifically within the crystalline lens and the lens capsule of the eyeis sufficient to produce optical breakdown and initiate aplasma-mediated ablation process. Near-infrared wavelengths for thelaser light are preferred because linear optical absorption andscattering in biological tissue is reduced for near-infraredwavelengths. As an example, the laser 64 can be a repetitively pulsed1031 nm device that produces pulses with less than 600 fs duration at arepetition rate of 120 kHz (+/−5%) and individual pulse energy in the 1to 20 micro joule range.

The cutting laser subsystem 44 is controlled by the control electronics54 and the user, via the control panel/GUI 56 and the user interfacedevices 58, to create a laser pulse beam 66. The control panel/GUI 56 isused to set system operating parameters, process user input, displaygathered information such as images of ocular structures, and displayrepresentations of incisions to be formed in the patient's eye 43.

The generated laser pulse beam 66 proceeds through a zoom assembly 68.The laser pulse beam 66 may vary from unit to unit, particularly whenthe UF laser 64 may be obtained from different laser manufacturers. Forexample, the beam diameter of the laser pulse beam 66 may vary from unitto unit (e.g., by +/−20%). The beam may also vary with regard to beamquality, beam divergence, beam spatial circularity, and astigmatism. Inmany embodiments, the zoom assembly 68 is adjustable such that the laserpulse beam 66 exiting the zoom assembly 68 has consistent beam diameterand divergence unit to unit.

After exiting the zoom assembly 68, the laser pulse beam 66 proceedsthrough an attenuator 70. The attenuator 70 is used to adjust thetransmission of the laser beam and thereby the energy level of the laserpulses in the laser pulse beam 66. The attenuator 70 is controlled viathe control electronics 54.

After exiting the attenuator 70, the laser pulse beam 66 proceedsthrough an aperture 72. The aperture 72 sets the outer useful diameterof the laser pulse beam 66. In turn the zoom determines the size of thebeam at the aperture location and therefore the amount of light that istransmitted. The amount of transmitted light is bounded both high andlow. The upper is bounded by the requirement to achieve the highestnumerical aperture achievable in the eye. High NA promotes low thresholdenergies and greater safety margin for untargeted tissue. The lower isbound by the requirement for high optical throughput. Too muchtransmission loss in the system shortens the lifetime of the system asthe laser output and system degrades over time. Additionally,consistency in the transmission through this aperture promotes stabilityin determining optimum settings (and sharing of) for each procedure.Typically to achieve optimal performance the transmission through thisaperture as set to be between 88% to 92%.

After exiting the aperture 72, the laser pulse beam 66 proceeds throughtwo output pickoffs 74. Each output pickoff 74 can include a partiallyreflecting mirror to divert a portion of each laser pulse to arespective output monitor 76. Two output pickoffs 74 (e.g., a primaryand a secondary) and respective primary and secondary output monitors 76are used to provide redundancy in case of malfunction of the primaryoutput monitor 76.

After exiting the output pickoffs 74, the laser pulse beam 66 proceedsthrough a system-controlled shutter 78. The system-controlled shutter 78ensures on/off control of the laser pulse beam 66 for procedural andsafety reasons. The two output pickoffs precede the shutter allowing formonitoring of the beam power, energy, and repetition rate as apre-requisite for opening the shutter.

After exiting the system-controlled shutter 78, the optical beamproceeds through an optics relay telescope 80. The optics relaytelescope 80 propagates the laser pulse beam 66 over a distance whileaccommodating positional and/or directional variability of the laserpulse beam 66, thereby providing increased tolerance for componentvariation. As an example, the optical relay can be a keplerian afocaltelescope that relays an image of the aperture position to a conjugateposition near to the xy galvo mirror positions. In this way, theposition of the beam at the XY galvo location is invariant to changes inthe beams angle at the aperture position. Similarly the shutter does nothave to precede the relay and may follow after or be included within therelay.

After exiting the optics relay telescope 80, the laser pulse beam 66 istransmitted to the shared optics 50, which propagates the laser pulsebeam 66 to the patient interface 52. The laser pulse beam 66 is incidentupon a beam combiner 82, which reflects the laser pulse beam 66 whiletransmitting optical beams from the ranging subsystem 46 and thealignment guidance subsystem 48.

Following the beam combiner 82, the laser pulse beam 66 continuesthrough a Z-telescope 84, which is operable to scan focus position ofthe laser pulse beam 66 in the patient's eye 43 along the Z axis. Forexample, the Z-telescope 84 can include a Galilean telescope with twolens groups (each lens group includes one or more lenses). One of thelens groups moves along the Z axis about the collimation position of theZ-telescope 84. In this way, the focus position of the spot in thepatient's eye 43 moves along the Z axis. In general, there is arelationship between the motion of lens group and the motion of thefocus point. For example, the Z-telescope can have an approximate 2×beam expansion ratio and close to a 1:1 relationship of the movement ofthe lens group to the movement of the focus point. The exactrelationship between the motion of the lens and the motion of the focusin the z axis of the eye coordinate system does not have to be a fixedlinear relationship. The motion can be nonlinear and directed via amodel or a calibration from measurement or a combination of both.Alternatively, the other lens group can be moved along the Z axis toadjust the position of the focus point along the Z axis. The Z-telescope84 functions as z-scan device for scanning the focus point of thelaser-pulse beam 66 in the patient's eye 43. The Z-telescope 84 can becontrolled automatically and dynamically by the control electronics 54and selected to be independent or to interplay with the X and Y scandevices described next.

After passing through the Z-telescope 84, the laser pulse beam 66 isincident upon an X-scan device 86, which is operable to scan the laserpulse beam 66 in the X direction, which is dominantly transverse to theZ axis and transverse to the direction of propagation of the laser pulsebeam 66. The X-scan device 86 is controlled by the control electronics54, and can include suitable components, such as a motor, galvanometer,or any other well known optic moving device. The relationship of themotion of the beam as a function of the motion of the X actuator doesnot have to be fixed or linear. Modeling or calibrated measurement ofthe relationship or a combination of both can be determined and used todirect the location of the beam.

After being directed by the X-scan device 86, the laser pulse beam 66 isincident upon a Y-scan device 88, which is operable to scan the laserpulse beam 66 in the Y direction, which is dominantly transverse to theX and Z axes. The Y-scan device 88 is controlled by the controlelectronics 54, and can include suitable components, such as a motor,galvanometer, or any other well known optic moving device. Therelationship of the motion of the beam as a function of the motion ofthe Y actuator does not have to be fixed or linear. Modeling orcalibrated measurement of the relationship or a combination of both canbe determined and used to direct the location of the beam.Alternatively, the functionality of the X-Scan device 86 and the Y-Scandevice 88 can be provided by an XY-scan device configured to scan thelaser pulse beam 66 in two dimensions transverse to the Z axis and thepropagation direction of the laser pulse beam 66. The X-scan and Y-scandevices 86, 88 change the resulting direction of the laser pulse beam66, causing lateral displacements of UF focus point located in thepatient's eye 43.

After being directed by the Y-scan device 88, the laser pulse beam 66passes through a beam combiner 90. The beam combiner 90 is configured totransmit the laser pulse beam 66 while reflecting optical beams to andfrom a video subsystem 92 of the alignment guidance subsystem 48.

After passing through the beam combiner 90, the laser pulse beam 66passes through an objective lens assembly 94. The objective lensassembly 94 can include one or more lenses. In many embodiments, theobjective lens assembly 94 includes multiple lenses. The complexity ofthe objective lens assembly 94 may be driven by the scan field size, thefocused spot size, the degree of telecentricity, the available workingdistance on both the proximal and distal sides of objective lensassembly 94, as well as the amount of aberration control.

After passing through the objective lens assembly 94, the laser pulsebeam 66 passes through the patient interface 52. As described above, inmany embodiments, the patient interface 52 includes a patient interfacelens 96 having a posterior surface that is displaced vertically from theanterior surface of the patient's cornea and a region of a suitableliquid (e.g., a sterile buffered saline solution (BSS) such as Alcon BSS(Alcon Part Number 351-55005-1) or equivalent) is disposed between andin contact with the posterior surface of the patient interface lens 96and the patient's cornea and forms part of an optical transmission pathbetween the shared optics 50 and the patient's eye 43.

The shared optics 50 under the control of the control electronics 54 canautomatically generate aiming, ranging, and treatment scan patterns.Such patterns can be comprised of a single spot of light, multiple spotsof light, a continuous pattern of light, multiple continuous patterns oflight, and/or any combination of these. In addition, the aiming pattern(using the aim beam 108 described below) need not be identical to thetreatment pattern (using the laser pulse beam 66), but can optionally beused to designate the boundaries of the treatment pattern to provideverification that the laser pulse beam 66 will be delivered only withinthe desired target area for patient safety. This can be done, forexample, by having the aiming pattern provide an outline of the intendedtreatment pattern. This way the spatial extent of the treatment patterncan be made known to the user, if not the exact locations of theindividual spots themselves, and the scanning thus optimized for speed,efficiency, and/or accuracy. The aiming pattern can also be made to beperceived as blinking in order to further enhance its visibility to theuser. Likewise, the ranging beam 102 need not be identical to thetreatment beam or pattern. The ranging beam needs only to be sufficientenough to identify targeted surfaces. These surfaces can include thecornea and the anterior and posterior surfaces of the lens and may beconsidered spheres with a single radius of curvature. Also the opticsshared by the alignment guidance: video subsystem does not have to beidentical to those shared by the treatment beam. The positioning andcharacter of the laser pulse beam 66 and/or the scan pattern the laserpulse beam 66 forms on the eye 43 may be further controlled by use of aninput device such as a joystick, or any other appropriate user inputdevice (e.g., control panel/GUI 56) to position the patient and/or theoptical system.

The control electronics 54 can be configured to target the targetedstructures in the eye 43 and ensure that the laser pulse beam 66 will befocused where appropriate and not unintentionally damage non-targetedtissue. Imaging modalities and techniques described herein, such asthose mentioned above, or ultrasound may be used to determine thelocation and measure the thickness of the lens and lens capsule toprovide greater precision to the laser focusing methods, including 2Dand 3D patterning. Laser focusing may also be accomplished by using oneor more methods including direct observation of an aiming beam, or otherknown ophthalmic or medical imaging modalities, such as those mentionedabove, and/or combinations thereof. Additionally the ranging subsystemsuch as an OCT can be used to detect features or aspects involved withthe patient interface. Features can include fiducials placed on thedocking structures and optical structures of the disposable lens such asthe location of the anterior and posterior surfaces.

In the embodiment of FIG. 3, the ranging subsystem 46 includes an OCTimaging device. Additionally or alternatively, imaging modalities otherthan OCT imaging can be used. An OCT scan of the eye can be used tomeasure the spatial disposition (e.g., three dimensional coordinatessuch as X, Y, and Z of points on boundaries) of structures of interestin the patient's eye 43. Such structure of interest can include, forexample, the anterior surface of the cornea, the posterior surface ofthe cornea, the anterior portion of the lens capsule, the posteriorportion of the lens capsule, the anterior surface of the crystallinelens, the posterior surface of the crystalline lens, the iris, thepupil, and/or the limbus. The spatial disposition of the structures ofinterest and/or of suitable matching geometric modeling such as surfacesand curves can be generated and/or used by the control electronics 54 toprogram and control the subsequent laser-assisted surgical procedure.The spatial disposition of the structures of interest and/or of suitablematching geometric modeling can also be used to determine a wide varietyof parameters related to the procedure such as, for example, the upperand lower axial limits of the focal planes used for cutting the lenscapsule and segmentation of the lens cortex and nucleus, and thethickness of the lens capsule among others. Additionally the rangingsubsystem such as an OCT can be used to detect features or aspectsinvolved with the patient interface. Features can include fiducialsplaced on the docking structures and optical structures of thedisposable lens such as the location of the anterior and posteriorsurfaces.

The ranging subsystem 46 in FIG. 3 includes an OCT light source anddetection device 98. The OCT light source and detection device 98includes a light source that generates and emits an OCT source beam witha suitable broad spectrum. For example, in many embodiments, the OCTlight source and detection device 98 generates and emits the OCT sourcebeam with a broad spectrum from 810 nm to 850 nm wavelength. Thegenerated and emitted light is coupled to the device 98 by a single modefiber optic connection.

The OCT source beam emitted from the OCT light source and detectiondevice 98 is passed through a pickoff/combiner assembly 100, whichdivides the OCT source beam into a sample beam 102 and a referenceportion 104. A significant portion of the sample beam 102 is transmittedthrough the shared optics 50. A relative small portion of the samplebeam is reflected from the patient interface 52 and/or the patient's eye43 and travels back through the shared optics 50, back through thepickoff/combiner assembly 100 and into the OCT light source anddetection device 98. The reference portion 104 is transmitted along areference path 106 having an adjustable path length. The reference path106 is configured to receive the reference portion 104 from thepickoff/combiner assembly 100, propagate the reference portion 104 overan adjustable path length, and then return the reference portion 106back to the pickoff/combiner assembly 100, which then directs thereturned reference portion 104 back to the OCT light source anddetection device 98. The OCT light source and detection device 98 thendirects the returning small portion of the sample beam 102 and thereturning reference portion 104 into a detection assembly, which employsa time domain detection technique, a frequency detection technique, or asingle point detection technique. For example, a frequency domaintechnique can be used with an OCT wavelength of 830 nm and bandwidth of100 nm.

Once combined with the UF laser pulse beam 66 subsequent to the beamcombiner 82, the OCT sample beam 102 follows a shared path with the UFlaser pulse beam 66 through the shared optics 50 and the patientinterface 52. In this way, the OCT sample beam 102 is generallyindicative of the location of the UF laser pulse beam 66. Similar to theUF laser beam, the OCT sample beam 102 passes through the Z-telescope84, is redirected by the X-scan device 86 and by the Y-scan device 88,passes through the objective lens assembly 94 and the patient interface52, and on into the eye 43. Reflections and scatter off of structureswithin the eye provide return beams that retrace back through thepatient interface 52, back through the shared optics 50, back throughthe pickoff/combiner assembly 100, and back into the OCT light sourceand detection device 98. The returning back reflections of the samplebeam 102 are combined with the returning reference portion 104 anddirected into the detector portion of the OCT light source and detectiondevice 98, which generates OCT signals in response to the combinedreturning beams. The generated OCT signals that are in turn interpretedby the control electronics to determine the spatial disposition of thestructures of interest in the patient's eye 43. The generated OCTsignals can also be interpreted by the control electronics to measurethe position and orientation of the patient interface 52, as well as todetermine whether there is liquid disposed between the posterior surfaceof the patient interface lens 96 and the patient's eye 43.

The OCT light source and detection device 98 works on the principle ofmeasuring differences in optical path length between the reference path106 and the sample path. Therefore, different settings of theZ-telescope 84 to change the focus of the UF laser beam do not impactthe length of the sample path for an axially stationary surface in theeye of patient interface volume because the optical path length does notchange as a function of different settings of the Z-telescope 84. Theranging subsystem 46 has an inherent Z range that is related to thelight source and detection scheme, and in the case of frequency domaindetection the Z range is specifically related to the spectrometer, thewavelength, the bandwidth, and the length of the reference path 106. Inthe case of ranging subsystem 46 used in FIG. 3, the Z range isapproximately 4-5 mm in an aqueous environment. Extending this range toat least 20-25 mm involves the adjustment of the path length of thereference path via a stage ZED, 106 within ranging subsystem 46. Passingthe OCT sample beam 102 through the Z-telescope 84, while not impactingthe sample path length, allows for optimization of the OCT signalstrength. This is accomplished by focusing the OCT sample beam 102 ontothe targeted structure. The focused beam both increases the returnreflected or scattered signal that can be transmitted through the singlemode fiber and increases the spatial resolution due to the reducedextent of the focused beam. The changing of the focus of the sample OCTbeam can be accomplished independently of changing the path length ofthe reference path 106.

Because of the fundamental differences in how the sample beam 102 (e.g.,810 nm to 850 nm wavelengths) and the UF laser pulse beam 66 (e.g., 1020nm to 1050 nm wavelengths) propagate through the shared optics 50 andthe patient interface 52 due to influences such as immersion index,refraction, and aberration, both chromatic and monochromatic, care mustbe taken in analyzing the OCT signal with respect to the UF laser pulsebeam 66 focal location. A calibration or registration procedure as afunction of X, Y, and Z can be conducted in order to match the OCTsignal information to the UF laser pulse beam focus location and also tothe relative to absolute dimensional quantities.

There are many suitable possibilities for the configuration of the OCTinterferometer. For example, alternative suitable configurations includetime and frequency domain approaches, single and dual beam methods,swept source, etc, are described in U.S. Pat. Nos. 5,748,898; 5,748,352;5,459,570; 6,111,645; and 6,053,613.

The system 2 can be set to locate the anterior and posterior surfaces ofthe lens capsule and cornea and ensure that the UF laser pulse beam 66will be focused on the lens capsule and cornea at all points of thedesired opening. Imaging modalities and techniques described herein,such as for example, Optical Coherence Tomography (OCT), and such asPurkinje imaging, Scheimpflug imaging, confocal or nonlinear opticalmicroscopy, fluorescence imaging, ultrasound, structured light, stereoimaging, or other known ophthalmic or medical imaging modalities and/orcombinations thereof may be used to determine the shape, geometry,perimeter, boundaries, and/or 3-dimensional location of the lens andlens capsule and cornea to provide greater precision to the laserfocusing methods, including 2D and 3D patterning. Laser focusing mayalso be accomplished using one or more methods including directobservation of an aiming beam, or other known ophthalmic or medicalimaging modalities and combinations thereof, such as but not limited tothose defined above.

Optical imaging of the cornea, anterior chamber, and lens can beperformed using the same laser and/or the same scanner used to producethe patterns for cutting. Optical imaging can be used to provideinformation about the axial location and shape (and even thickness) ofthe anterior and posterior lens capsule, the boundaries of the cataractnucleus, as well as the depth of the anterior chamber and features ofthe cornea. This information may then be loaded into the laser 3-Dscanning system or used to generate a three dimensionalmodel/representation/image of the cornea, anterior chamber, and lens ofthe eye, and used to define the cutting patterns used in the surgicalprocedure.

Observation of an aim beam can also be used to assist in positioning thefocus point of the UF laser pulse beam 66. Additionally, an aim beamvisible to the unaided eye in lieu of the infrared OCT sample beam 102and the UF laser pulse beam 66 can be helpful with alignment providedthe aim beam accurately represents the infrared beam parameters. Thealignment guidance subsystem 48 is included in the assembly 62 shown inFIG. 3. An aim beam 108 is generated by an aim beam light source 110,such as a laser diode in the 630-650 nm range.

Once the aim beam light source 110 generates the aim beam 108, the aimbeam 108 is transmitted along an aim path 112 to the shared optics 50,where it is redirected by a beam combiner 114. After being redirected bythe beam combiner 114, the aim beam 108 follows a shared path with theUF laser pulse beam 66 through the shared optics 50 and the patientinterface 52. In this way, the aim beam 108 is indicative of thelocation of the UF laser pulse beam 66. The aim beam 108 passes throughthe Z-telescope 84, is redirected by the X-scan device 86 and by theY-scan device 88, passes through the beam combiner 90, passes throughthe objective lens assembly 94 and the patient interface 52, and on intothe patient's eye 43.

The video subsystem 92 is operable to obtain images of the patientinterface and the patient's eye. The video subsystem 92 includes acamera 116, an illumination light source 118, and a beam combiner 120.The video subsystem 92 gathers images that can be used by the controlelectronics 54 for providing pattern centering about or within apredefined structure. The illumination light source 118 can be generallybroadband and incoherent. For example, the light source 118 can includemultiple LEDs. The wavelength of the illumination light source 118 ispreferably in the range of 700 nm to 750 nm, but can be anything that isaccommodated by the beam combiner 90, which combines the light from theillumination light source 118 with the beam path for the UF laser pulsebeam 66, the OCT sample beam 102, and the aim beam 108 (beam combiner 90reflects the video wavelengths while transmitting the OCT and UFwavelengths). The beam combiner 90 may partially transmit the aim beam108 wavelength so that the aim beam 108 can be visible to the camera116. An optional polarization element can be disposed in front of theillumination light source 118 and used to optimize signal. The optionalpolarization element can be, for example, a linear polarizer, a quarterwave plate, a half-wave plate or any combination. An additional optionalanalyzer can be placed in front of the camera. The polarizer analyzercombination can be crossed linear polarizers thereby eliminatingspecular reflections from unwanted surfaces such as the objective lenssurfaces while allowing passage of scattered light from targetedsurfaces such as the intended structures of the eye. The illuminationmay also be in a dark-field configuration such that the illuminationsources are directed to the independent surfaces outside the capturenumerical aperture of the image portion of the video system.Alternatively the illumination may also be in a bright fieldconfiguration. In both the dark and bright field configurations, theillumination light source may be used as a fixation beam for thepatient. The illumination may also be used to illuminate the patient'spupil to enhance the pupil iris boundary to facilitate iris detectionand eye tracking. A false color image generated by the near infraredwavelength or a bandwidth thereof may be acceptable.

The illumination light from the illumination light source 118 istransmitted through the beam combiner 120 to the beam combiner 90. Fromthe beam combiner 90, the illumination light is directed towards thepatient's eye 43 through the objective lens assembly 94 and through thepatient interface 94. The illumination light reflected and scattered offof various structures of the eye 43 and patient interface travel backthrough the patient interface 94, back through the objective lensassembly 94, and back to the beam combiner 90. At the beam combiner 90,the returning light is directed back to the beam combiner 120 where thereturning light is redirected toward the camera 116. The beam combinercan be a cube, plate, or pellicle element. It may also be in the form ofa spider mirror whereby the illumination transmits past the outer extentof the mirror while the image path reflects off the inner reflectingsurface of the mirror. Alternatively, the beam combiner could be in theform of a scraper mirror where the illumination is transmitted through ahole while the image path reflects off of the mirrors reflecting surfacethat lies outside the hole. The camera 116 can be an suitable imagingdevice, for example but not limited to, any silicon based detector arrayof the appropriately sized format. A video lens forms an image onto thecamera's detector array while optical elements provide polarizationcontrol and wavelength filtering respectively. An aperture or irisprovides control of imaging NA and therefore depth of focus and depth offield and resolution. A small aperture provides the advantage of largedepth of field that aids in the patient docking procedure.Alternatively, the illumination and camera paths can be switched.Furthermore, the aim light source 110 can be made to emit infrared lightthat would not be directly visible, but could be captured and displayedusing the video subsystem 92.

FIG. 4 is a flow chart of a method 400 in which force feedback is usedto secure a patient to the patient interface 52 of the laser eye surgerysystem 2, according to embodiments of the present invention. In a step410, a suction ring, for example suction ring 122 described below, iscoupled to the patient's eye 43. In a step 420, the vertical position ofthe patient interface 52 of the laser eye surgery system 2 is displayed,for example, on the touch-screen control panel 12, any display connectedto the external connections 22 or USB data ports 30, and/or the controlpanel/GUI described above. In a step 430, the patient chair 6 of thelaser eye surgery system 2 is moved to position the suction ring forcoupling with a disposable lens cone, for example disposable lens cone124 described below. In a step 440, the suction ring is coupled to thedisposable lens. In a step 450, the magnitudes and directions of theeye-to-patient interface forces are displayed, for example, on thetouch-screen control panel 12, any display connected to the externalconnections 22 or USB data ports 30, and/or the control panel/GUIdescribed above. These eye-to-patient interface forces are measured andcalculated for as described below and will typically include forces inthe vertical as well as lateral directions. In a step 460, the patientchair 6 is moved to vertically position the patient interface 52 foractuation of a position locking device 126 used to secure the patientinterface 52 in a desired treatment vertical position. In a step 470, arange of vertical movement of the patient interface 52 above and belowthe treatment vertical position is accommodated while constant verticalforce between the patient's eye 43 and the interface 52 is maintained.In a step 480, the upward movement of the patient chair 6 is limitedbased on the vertical position of the patient interface 52. In a step490, the position locking device 126 is actuated to secure the positionof the patient interface 52 for treatment.

Although the above steps show method 400 of treating a patient inaccordance with embodiments, a person of ordinary skill in the art willrecognize many variations based on the teaching described herein. Thesteps may be completed in a different order. Steps may be added ordeleted. Some of the steps may comprise sub-steps. Many of the steps maybe repeated as often as if beneficial to the treatment.

FIGS. 5A-5E show a method by which the patient's eye 43 is secured tothe patient interface 52 of the laser eye surgery system 2 according toembodiments of the present invention.

FIG. 5A shows a preliminary step of coupling the patient's eye 43 with asuction cup 122. The patient will typically be resting on a top side ofthe patient support bed 34, which as shown by arrow 140 can be movedlaterally in both the X and Y directions as well as vertically in the Zdirection as shown by arrow 142. The suction cup 122 may comprise anannular vacuum ring to couple to the eye with suction and a secondvacuum line to apply suction to a lens placed over the eye.

The patient interface 52 may comprise a component of a patient interfaceassembly 160. The patient interface assembly 160 may comprise thehousing 134, the patient interface 52, and the counterweight 128, forexample. The patient interface assembly may comprise a guide 162, forexample a guide formed with a channel in the housing, so as to allowmovement of the patient interface along an axis 164, typically avertical axis. Such vertical movement is facilitated by a counterweight128 which is housed within 132 and coupled to the patient interface 52via cable assembly 130. The counterweight 128 may comprise a componentof a counterweight assembly 165 which may comprise the housing 132 and aguide 166 so as to allow movement of the counterweight 128 along an axis168, typically a vertical axis. The housing 134 of the patient interfaceassembly 160 also comprises a linear encoder 136 to determine thevertical position of the housing assembly 52. The housing 134 furthercomprises a locking mechanism 126 which can be actuated to lock thepatient interface 52 at a desired vertical position. In manyembodiments, the counterweight 128 biases the patient interface 52 to beat this desired vertical position. When the patient interface 52 is atthe desired vertical position, the locking mechanism 126 can lock intoreceptacle 138 in the patient interface 52. The locking mechanism 126may comprise one or more of a detent, a lock and key mechanism, anopening to receive a linear protrusion, or a rotating cam, a flatsurface to receive a friction brake. The friction brake may beconfigured to break free from the flat surface if the vertical forcefrom the patient interface 52 surpasses a threshold limit that would beconsidered dangerous to the patient. The patient interface 52 comprisesa disposable lens cone 124 which is configured to couple to the suctioncup 122. The disposable lens cone 124 is coupled to the main body of thepatient interface 52 via coupler 146. The patient interface 52 comprisesa plurality of force transducers 144 disposed between the main body ofthe patient interface 52 and the coupler 146. Typically, the forcetransducers 144 will lie in the same horizontal plane normal to thevertical axis 164 of the patient interface 52 and parallel to thesuction cup 122 and the disposable lens cone 124. The force transducers144 detect the amount of vertical force between the main body of thepatient interface 52 and the coupler 146, including the force betweenthe patient interface 52 and the patient's eye 43, when the suction cup124 is coupled to both the patient's eye 43 and the disposable lens cone124. The force transducers 144 can transmit data regarding measuredforce via communications paths 60 to the other subsystems of the lasereye surgery system 2 including the control electronics 54, the controlpanel/GUI 56, and the user interface devices 58.

As shown in FIG. 5B, once the suction cup 122 is coupled to thepatient's eye 43, the suction cup 122 can be coupled to the disposablelens cone 124 to couple the patient's eye 43 to the interface assembly52. Because the patient is resting on and secured to the patient supportbed 36, the position of the patient's eye 43 can be varied laterally inthe X and Y directions as shown by arrow 142A as well as in thevertically in the Z direction as shown by arrow 140A by varying theposition of the patient support bed 34 relative to the base 32, forexample, by adjusting the patient chair joystick control 38 whichadjusts a linkage 35 of the patient chair 6.

As shown in FIG. 5C, the patient interface 52 can be moved verticallyand locked in place at a desired position by actuating locking mechanism126. The patient is seated onto the patient support bed 36 and thepatient's eye 43 is coupled the patient interface 52 so that the patientinterface 52 will typically be moved upward by moving the patientsupport bed 36 upward. When the linear encoder 136 detects that thepatient interface 52 is in the desired vertical position, the linearencoder 136 will send a signal to the control electronics 52 to indicatethat the patient interface 52 is in the desired vertical position. Thelocking mechanism 126 may then lock the patient interface 52 in thedesired vertical position. The control electronics 54 may then limit orprevent further upward movement of the patient support bed 34 to preventany injury to the patient's eye 34 that may occur if the patient supportbed 34 is moved up while the patient interface 52 remains in place,which would otherwise sandwich the patient's eye 43. While the patientsupport bed 34 is limited or prevented from further upward movement,lateral movement of the patient support bed 34 will typically beunrestricted.

The patient interface 52 comprises at least three force transducers 144.The force transducers 144 measure force in the Z-direction. Becausethere will typically be at least three force transducers 144, the forcedifferential between the transducers can be used to calculate themagnitude and direction of the forces between the patient interface 52and the patient's eye 43 in the X, Y, and Z directions. For example, thepatient interface 52 may send the force data from the force transducers144 to the control electronics 54 which in turn calculates the forcebetween the patient interface 52 and the patient's eye 43 in the X, Y,and Z directions. As discussed above with regard to method 400, thecalculated patient interface to eye forces can be displayed and thelaser eye surgery system operator can adjust the position of the patientsupport bed 36 via patient chair joystick control 38 so that the patientinterface to eye forces remain constant over the course of a laser eyesurgical procedure. For example, the laser surgery system operator canview the displayed forces and through the patient chair control inputdevice 38, adjust the position of the patient support bed 36. In manyembodiments, this procedure can be automated. For example, the controlelectronics 52 may calculate the patient interface to eye forces in theX, Y, and Z directions and automatically adjust the position of thepatient support bed 36 accordingly as in method 900 described below.

As shown in FIG. 5D, the patient interface 52 can be moved upward withinthe housing 134 beyond the position the patient interface 52 would be inif locked into position by locking mechanism 126, giving the patientinterface 52 some vertical leeway within the housing 134 as the patientinterface 52 is moved into the desired vertical position.

FIG. 5E shows the patient interface 52 locked into the desired verticalposition by locking mechanism 126. As discussed above, the forcetransducers 144 detect the vertical forces (represented by arrows 150)between the patient interface 52 and the patient's eye 43.

FIG. 6 shows a cross-section of the patient interface 52 taken alongline 151 shown in FIG. 5E. As discussed above, the patient interface 52comprises a plurality of force transducers 144. The force transducers144 are positioned equidistant from a central vertical axis 152 of thepatient interface 52 and are equidistant from one another as well. Theforce transducers 144 measure the forces between the patient interface52 and the patient's eye 43 along the vertical axis 164. The forcedifferentials between the force transducers 144 are used to calculatethe lateral forces between the patient interface 52 and the patient'seye 43, i.e., the X-direction as shown by arrow 153 and the Y-directionas shown by arrow 154.

FIG. 7 is a simplified block diagram of subsystem of the laser eyesurgery system 2 used to monitor and control the position of thepatient's eye relative to the patient interface. The patient interfaceforce sensors 144 are coupled to the control electronics 54. Asdiscussed above, the patient interface force sensors 144 measure forcesand send the measurement data to the control electronics 54. The patientinterface linear encoder 136 tracks the vertical position of the patientinterface 52 and sends the position data to the control electronics 54.The control electronics 54 may then send the force and position data toanother subsystem of the laser eye surgery system 2 to be displayed tothe operator of the laser eye surgery system 2. The control electronics54 are also coupled to the patient chair control input device 38, whichwill typically be a joystick, and also to the patient chair 6. Theoperator of the laser eye surgery system 2 can send instructions throughthe control electronics to adjust the position of the patient chair 6.As discussed above with regard to FIG. 5C, the position of the patientchair 6 can be adjusted so the forces and vertical position of thepatient interface 52 relative to the patient's eye 43 can be heldsubstantially constant over the course of a laser eye surgicalprocedure.

FIG. 8 is a flow chart illustrating a procedure 800 to adjust the lasereye surgery system 2. In addition to measuring forces in threedimensions and the vertical position of the patient interface 52, thepatient interface 52 and its force transducers 144 can be used todetermine the movements of the patient's eye 43 and the laser eyesurgery system 2 can be adjusted accordingly. In a step 810, the eye topatient interface forces are monitored. In a step 820, the relativemovement of a targeted eye location is calculated based on the eye topatient interface forces and stiffness characteristics of the patientinterface and optionally the eye. In a step 830, the laser targetlocations are adjusted based on the calculated relative eye movement.

FIG. 9 is a flow chart illustrating a method 900 to position of thepatient's eye 43 relative to the patient interface 52. As discussedabove with reference to FIG. 5C, the control electronics 52 of the lasereye surgery system 2 may calculate the magnitudes and directions of thepatient interface to eye forces and automatically adjust the position ofthe patient support bed 36 accordingly. FIG. 9 shows a method 900 inwhich such calculation and automatic adjustment is performed. In a step910, the suction ring 122 is coupled to the patient's eye 43. In a step920, the vertical position of the patient interface 52 is monitored. Ina step 930, the patient chair 6 is moved to position the suction ring122 for coupling with the disposable lens 124. In a step 940, thesuction ring 122 is coupled to the disposable lens 940. In a step 950,the eye to patient interface forces are monitored. In a step 960, thepatient chair 6 is automatically moved to vertically position thepatient interface 52 for actuation of the position locking device 126 inresponse to the patient interface forces and the vertical position ofthe patient interface 52. In a step 970, a range of vertical movement ofthe patient interface 52 is accommodated above and below the treatmentvertical position while maintaining a constant vertical interface force.In a step 980, the position locking device 126 is actuated to secure theposition of the patient interface 52 for treatment of the patient. Asdiscussed above, when the patient interface 52 is secured, the furtherupward movement of the patient chair 6 may be limited or restricted toprevent injury to the patient's eye while lateral movement of thepatient chair 6 remains unrestricted.

Although the above steps show method 900 of treating a patient inaccordance with embodiments, a person of ordinary skill in the art willrecognize many variations based on the teaching described herein. Thesteps may be completed in a different order. Steps may be added ordeleted. Some of the steps may comprise sub-steps. Many of the steps maybe repeated as often as if beneficial to the treatment.

One or more of the steps of the method 900 may be performed with thecircuitry as described herein, for example one or more of the processoror logic circuitry such as the programmable array logic for fieldprogrammable gate array. The circuitry may be programmed to provide oneor more of the steps of method 900, and the program may comprise programinstructions stored on a computer readable memory or programmed steps ofthe logic circuitry such as the programmable array logic or the fieldprogrammable gate array, for example.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A laser eye surgery system, comprising: a patient support; a patient interface assembly comprising a housing and a patient interface disposed within the housing so as to be vertically movable within the housing, wherein the patient interface is configured for coupling to an eye of a patient, the patient interface having an axis alignable with the eye of the patient, the patient interface comprising at least three force transducers to monitor forces between the eye of the patient and the patient interface and in response thereto to output force data; and a controller which is configured to receive the force data from each of the force transducers and to ascertain therefrom: a first force between the eye of the patient and the patient interface along the axis of the patient interface, a second force between the eye of the patient and the patient interface in a first direction transverse to the axis and a third force between the eye of the patient and the patient interface in a second direction transverse to the axis, the controller being coupled to the patient support and further being configured to move the patient support along the axis and transverse to the axis in response to the ascertained forces, wherein the controller embodies instructions of a program which is executed by the controller to move the patient support along the axis and in the first direction transverse to the axis and the second direction transverse to the axis in response to the ascertained forces so as to maintain each of the first, second, and third forces between the eye of the patient and the patient interface within a desired range.
 2. The laser eye surgery system of claim 1, wherein the patient support comprises a base and a linkage to move the patient support along the axis and transverse to the axis in response to the controller.
 3. The laser eye surgery system of claim 2, wherein the patient support comprises a movable patient chair having a patient seating area movable relative to the base.
 4. The laser eye surgery system of claim 1, further comprising a display for displaying the ascertained forces along the axis, the first direction and the second direction as a three dimensional vector.
 5. The laser eye surgery system of claim 1, further comprising a laser configured to deliver pulses of a laser beam to the eye of the patient to treat the eye of the patient, wherein the controller further embodies instructions of a program which is executed by the controller to offset the pulses of the laser beam in response to forces of the plurality of transducers to increase an accuracy of a placement of the laser beam pulses on the eye.
 6. The laser eye surgery system of claim 1, wherein the controller further embodies instructions of a program which is executed by the controller to allow movement of the patient support along the first direction and the second direction transverse to the axis to decrease force to the eye.
 7. The laser eye surgery system of claim 1, further comprising a counter-weight coupled to the patient interface to facilitate vertical movement of the patient interface.
 8. The laser eye surgery system of claim 1, wherein the axis of the patient interface extends in a vertical direction and wherein the patient interface is adapted to move upward by upward movement of the patient support when the patient is placed on the patient support and the eye of the patient is coupled to the patient interface.
 9. The laser eye surgery system of claim 1, further comprising a locking mechanism adapted to lock a vertical position of the patient interface when the patient interface has reached a desired vertical position.
 10. The laser eye surgery system of claim 9, wherein the locking mechanism comprises one or more of a detent, a lock and key mechanism, an opening to receive a linear protrusion, a rotating cam, or a flat surface to receive a friction brake.
 11. The laser eye surgery system of claim 1, further comprising a counter-weight coupled to the patient interface via a cable assembly, the counter-weight being configured to move along a vertical axis and being configured to bias the patient interface to be at a desired vertical position.
 12. The laser eye surgery system of claim 1, wherein the patient interface includes a receptacle and wherein the housing comprises: a linear encoder configured to track a vertical position of the patient interface and to send to the controller position data indicating the vertical position, and a locking mechanism, wherein the controller is configured to move the patient support in response to the calculated forces and the tracked vertical position of the patient interface, the linear encoder is configured to indicate to the controller when the patient interface is in a desired vertical, and the locking mechanism is configured to be activated to engage the receptacle in the patient interface when the patient interface is in a desired vertical position and to lock the patient interface in the desired vertical position.
 13. The laser eye surgery system of claim 12, further comprising a display configured to display the force data and the position data to an operator of the laser eye surgery system.
 14. The laser eye surgery system of claim 12, wherein the controller is configured to move the patient support in the first direction and in the second direction while the patient interface is locked in the desired vertical position.
 15. The laser eye surgery system of claim 8, further comprising a laser configured to deliver pulses of a laser beam to the eye of the patient to treat the eye of the patient, wherein the controller is configured to control movement of the patient support so that the ascertained forces remain constant over a course of a laser eye surgical procedure performed with the laser. 